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Visual System

開催日 2014/9/12
時間 11:00 - 12:00
会場 Poster / Exhibition(Event Hall B)

Subspace mapping in Gabor wavelet domain for Macaque V2 and MT neurons

  • P2-141
  • 橋本 肇 / Hajime Hashimoto:1 佐々木 S 耕太 / Kota S Sasaki:1,2 稲垣 未来男 / Mikio Inagaki:1 大澤 五住 / Izumi Ohzawa:1,2 
  • 1:大阪大学生命機能研究科 / Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan 2:脳情報通信融合研究センター(CiNet) / Center for Information and Neural Networks (CiNet), Osaka, Japan 

Although both V2 and MT receive dominant afferent inputs from V1, they play different roles in separate visual streams (i.e. "what" and "where" pathways). What inputs from V1 contribute to differentiating the function of single neurons between these areas? To study neurons in multiple areas even in separate streams, we devised dynamic Gabor wavelet noise stimulus so that simple cells in V1 can be excited and inhibited randomly in a highly controlled and efficient manner. Each video frame of this stimulus was constructed by adding many 3D Gabor elements, each of which resembles the spatiotemporal receptive field of a simple cell. This stimulus efficiently covers the vast parameter space defined by horizontal and vertical positions, time, orientation, spatial frequency, temporal frequency, and phase. Single-unit activity was recorded in anesthetized macaque V2 and MT during the presentation of the dynamic Gabor wavelet noise stimulus. Gabor elements responsible for the responses were estimates by correlating Gabor elements with recorded spikes (reverse correlation). We found that V2 and MT neurons collect inputs from V1 in different fashions. The majority of V2 neurons share functional characteristics with standard V1 model cells; they showed uniform tuning to orientation and spatial frequency within the spatial receptive field. Our linear analysis did not find selectivity to curvature or angle (i.e. inhomogeneous orientation tuning in the spatial receptive field) in V2 neurons. Some MT neurons, on the other hand, showed suppressed responses to the anti-preffered direction of motion in addition to the functional characteristics of standard V1 model cells.

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